The present invention relates to a braking system and manual retractor for use in a wide range of applications. It is especially suited for use in a combined service and handbrake control system for hydraulic disc brakes. In the preferred embodiment of the invention, the actuator has been used on a mass transit or rapid transit car.
In particular, the present invention is intended for use with a disc brake having a conventional service brake actuator and a spring applied handbrake, both of which are adapted to control braking torque through a single brake head. In addition, the present invention is applicable to braking systems which employ separate brake heads with a two-stage converter. In these converters, a fluid restrained spring motor is used to apply the parking brakes and emergency brakes by venting the fluid motor.
While spring applied parking brakes and emergency brakes have been used in the prior art as a fail-safe actuator for a friction brake system, they do present problems in releasing the brake or compressing the spring in the event of a brake system malfunction. If the system has malfunctioned, and no fluid pressure or hydraulic pressure is available to retract the brake, then a separate means must be provided for mechanically retracting the spring motor. Similarly, if the spring applied brakes are used on a vehicle without an independent fluid pressure supply source, the actuation of the spring applied brake when the car is disconnected from the train will require a separate means of retracting the brake before the vehicle can be moved.